The novel feature of this question is that Mo has never used Powerpoint or, perhaps, any other presentation/ slideshow software. So if he has to learn some new software, in 2018, what would be most useful in the future? Powerpoint 2007?

Powerpoint is easy to use, and will do the job, but the fact that it's already on his computer doesn't seen to me to be a good reason to use it.

The best reason to use Powerpoint is that lots of people know it, so he can get help and folk can contribute. Others have said that using an old version should not be a problem. The disadvantage is that it's proprietary software, expensive (if he ever needs to update it) and only does one thing - build presentations.

I agree with what Jack said about html in a browser being the most flexible and portable way to show a presentation. It lacks some of the fancy features of Powerpoint, such as transitions between slides* but it has one big advantage: you can use it to build websites too. And posters. And ...

I'm not aware of any easy free software specifically aimed at building presentations in html - as opposed to websites. Anybody? I know that any html editor would do, but for a beginner and aimed at multimedia slides?

But the key question for Mo might be: what sort of software would you rather become familiar with?

*You can do transitions and stuff in html but it's complicated and unnecessary.